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Are Air Source Heat Pumps Any Good In Winter

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  • 15-11-2021
Are Air Source Heat Pumps Any Good In Winter

A common question regarding air source heat pumps is: are air source heat pumps any good in winter? This article explores the performance of this heating system in colder months.

Can I Use A Heat Pump In Winter

Air source heat pumps can be used all year round to provide efficient and cost-effective renewable energy to heat your home. These systems can continue to use outside air as a heat source even at temperatures reaching -25°C. However, there are many ways to boost your air source heat pump during the cold winter months to ensure your house stays warm and comfortable.

How Warm Can A Heat Pump Get Your House?

How Air Source Heat Pumps Work

Air source heat pumps (ASHPs) take air from outside of your home and use it to generate heat for your central heating throughout the year, even during the colder months. 

The ASHP unit itself sits outside your home and draws air into the system using a rotating fan. After the air has entered the system, it begins the heating process. 

This outside air is forced over an exchanger coil containing a refrigerant liquid. The refrigerant then boils, in a reverse process of what a fridge does, and changes state into a gas. 

The gas is then forced into a compressor, raising its temperature even further through additional pressure. This warm gas is then passed over the water or air inside your central heating system, warming it up and sending it through your house. 

While this heating system is a little more complicated than more traditional boiler-fed central heating, there are numerous benefits to having an air source heat pump installed in your home


This can include:

  • High-efficiency heating of your home.
  • Reducing your monthly heating bills.
  • Payments from the UK Government under the Renewable Heat Incentive (RHI).
  • Long lifespan of 25 years.
  • Easy-to-no maintenance required.

Therefore you can see that these air source heat pumps are an efficient, reliable and cost-effective method of heating your home right the year round. 

However, while they are thoroughly efficient heating systems, you may need to perform certain modifications to your home to help them work the best they can through December, January and February.

How Good Are Heat Pumps In Cold Weather?

Even though we know how these pumps generate the heat necessary to warm your house, you might still wonder how they can do this when it's cold outside. Even when the weather is below freezing, your air or ground source heat pumps can still generate enough warmth to keep your home comfortable through the winter. 

Here in the UK, the ground temperature rarely falls below 10 °C, and while this would feel especially cold to us, even at this temperature, there is still some warmth the heat pump can derive from the ground to warm your home. Therefore, despite how cold it might feel outside, your heat pump system can still keep your home comfortable.

Even if you have an air source heat pump, it can still generate enough heat to keep you cosy regardless of how cold it might feel outside when there is no warm air. It is important to remember that while we humans may measure the outside temperature at 0 °C, this is an artificial scale. Even at these average low temperatures, there is still ambient heat in the air to power your ASHP.

Naturally, the ability of your heat pump to provide enough warmth for your property during the winter months depends on the type of heat pump you buy. They are not all alike, and some will be more efficient during the colder months than others. Therefore, you must purchase the right heat pump for your home. 

The UK does not have a drastic climate during the winter compared to other countries. Northern America and Canada experience far colder winters than we do, with temperatures falling to a numbing -30 °C. Therefore, since most heat pumps on the market are manufactured and tested in Germany by companies such as Viessmann, they should operate perfectly in the UK climate. 

How Efficient Is A Heat Pump In Cold Weather?

Naturally, while your heat pump will be able to handle the mild UK winter, any dramatic temperature drops will still have an effect. Mainly, colder days mean that your heat pump has to work harder, meaning a drop in your heat pump's efficiency. This is because more electricity is required to generate the same amount of heat.

How Efficient Is A Heat Pump In Cold Weather

Coefficient of Performance

Efficiency in heat pumps is measured through a Coefficient of Performance, or CoP. This measurement tracks the amount of electricity input into the pump compared to the amount of heat output. For example, if you put 1 kW of electricity into the pump and produce 3 kW of heat, it will have a CoP measurement of 3. In essence, the higher the CoP measurement, the more efficient your heat pump is.

For example, if you have an outdoor temperature of around 8 °C, a heat pump installed in your property could reach a CoP of around 3. However, if the temperature were to drop to -8 °C, the pumps Coefficient of Performance might fall to 1 or 2. If the temperature falls further than this to extremely low temperatures, you may need a backup heating system.

However, extremely low temperatures are very rare in the UK, meaning a heat pump is more than capable of providing enough heat for your home. It is only in extremely cold climates, like those previously mentioned in Canada and North America, where backup systems might be needed. However, this is an expensive option. Therefore a heat pump could not be the best way to heat your home if you live in an extremely cold climate. 

Ground Source Heat Pump

If the winter temperatures you live in can reach dramatically low levels, then it may be best to invest in a ground source heat pump rather than an air source one. Ground temperatures do not fall as low as air temperatures, meaning a ground source heat pump will not require as much electricity to heat your home. 

Naturally, as with any other essential home appliance, regular maintenance and servicing are key. It is usually recommended that you have your heat pump serviced once a year. These regular check-ups will give you peace of mind knowing your heat pump is operating safely and is capable of providing enough heat for your home during the winter months.

If you have an air source heat pump installed, an important part of this maintenance is clearing the unit of any debris that might fall into it. This can block the fans inside the unit, preventing them from generating any heat. Therefore, to ensure continued efficiency, you should clear your ASHP unit and its air filters regularly. Naturally, if you notice any more serious issues will your heat pump, call a qualified engineer. 

Tips For Using A Heat Pump In Winter

As previously mentioned, regardless of how cold it might feel outside during the winter, your heat pump can still generate enough heat to warm your home efficiently. However, there are a few things you can do to help it in its job. Here are a few tips for using your heat pump in winter.

Some people might think that they need to cover their air source heat pump during the winter to prevent freezing, but this is the opposite of what you should do. Covering the heat pump will block the airflow, meaning it won't be able to do its job and heat your home. Most modern heat pumps come with a defrost mode to prevent any cold damage from occurring.

Smart thermostats are an essential addition to any central heating system, not just for those who rely on a heat pump. Smart thermostats allow you to better control the temperature in your home, with more accurate temperature settings than other systems. This accuracy allows you to heat your home more efficiently, helping to keep your monthly energy costs down.


Again, keeping your air source heat pump free of any obstructions is an essential part of its maintenance. In the same way that you should not cover it up during the winter, you will need to ensure that it is free of any snow, leaves, or other debris. When the airflow is obstructed, your heat pump can't operate as efficiently. Therefore it is important to clear it of debris regularly.


Given that heat pumps run on electricity, you could find a cheaper energy supplier if you want to have a truly efficient system. Some air source heat pumps can operate at efficiencies of up to 300%, but paying through the nose for electricity won't feel like much of a benefit. Therefore, finding the cheapest tariff for your electricity will help you during the wintertime.

There is no point heating your home if the warmth will only escape through your poorly insulated walls and roof. Therefore, if you want to heat your home as efficiently as possible, ensuring that your home is well insulated is the best way to go. Additionally, it will take far longer to warm your home to a satisfactory level without proper insulation, running up your energy bills.


The method by which an ASHP generates heat for your central heating means they cannot generate as much heat as a traditional gas boiler. While they still operate through "wet systems", by generating hot water to send through your radiators to warm your home, installing larger radiators or underfloor heating is the best way to get the most from your heat pump.


Ensuring that your heat pump is in prime condition before the winter sets in is also a good way to keep it running efficiently when you need it most. Calling a professional heating engineer to inspect your heat pump at the end of summer or during the autumn will ensure your heat pump is ready for the cold temperatures of winter.

Are you considering air source heat pump installation in Essex, Suffolk and the surrounding areas? We have years of experience in providing tailored energy-efficient and affordable home heating solutions. So if you need any further assistance  with air source heat pumps, follow the link below.